Stretch yarns and fabrics with multiple elastic yarns

ABSTRACT

Included herein is an articles and methods including a core spun yarn. The core spun yarn includes a sheath of hard fibers and two sets of elastic fibers wherein the sets of elastic fibers have different properties. The properties may differ in one or more ways such as having a different denier, composition or draft. One or both of the sets of elastic fibers can be precovered.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the manufacture of stretch composite yarns andfabrics. It specifically relates to the fabrics and methods includingtwo sets of elastic core fibers within one yarn.

2. Summary of Related Art

Stretch fabrics with elastic composite yarn have been on the markets forlong time. Fabric and garment manufacturers generally know how to makefabrics with the right quality parameters to achieve fabrics acceptableto consumers. In current commercially available fabrics, only oneelastic fiber system exists inside yarn and fabrics. One elastic fiberprovides double functions: stretch and recovery. It is difficult toobtain the fabrics which have easy stretch, high recovery and lowshrinkage performance.

Easy stretch is one important characteristic for comfort garment. Forgarment with greater comfort, the fabric can be easy stretched out whengarment is put on human body and move. They have low pressure exerted onthe body by garment. The garment can be cut to achieve a morestreamlined appearance and can conform better to the body, while stillmaintaining comfort for wearer in motion. Such performance can beachieved through low fabric tensile modulus by minimizing the garment'sresistance to the body's demands in movement.

However, for the fabric with low tensile modulus, a typical qualityissue is that the fabric can't quickly recovery to original size andshape after fabrics are over stretched out in some parts of the body,such as in knee, butt and waist, particularly for the fabrics with highstretch level. Usually, the fabric has low recovery power when thetensile modulus is low. Consumers see baggy and saggy issues after longtime wear.

In contrast, in order to get fabric with good recovery, extracontractive force needed within fabrics. Higher content or more powerfulelastic fiber could be added to fabrics. However, these fabrics havehigh extension modulus and higher restrict force. Consumers complainhigher garment pressures and uncomfortable restriction during wearingand movement. In the same time, the fabric has poor dimension stability.Heatset is a necessary processing to control the fabric shrinkage. Thegarment comfort and freedom of movement are compromised by fabric shaperetention and recovery function. The fabrics having easy stretch, highrecovery and low shrinkage performance are still desired.

For many years, composite elastic yarns are well known. For example, byU.S. Pat. Nos. 4,470,250, 4,998,403, 7,134,265, 6,848,151, theelastomeric fibers, such as spandex, have been covered with relativelyinelastic fibers in order to facilitate acceptable processing forknitting or weaving, and to provide elastic composite yarns withacceptable characteristics for various end-use fabrics. In US patentapplication US 2008/0268734A1 and USA 200810318485A1, a rigid filamentis used, together with elastic filaments, as core inside core spun yarn.

Therefore, there is a need to produce stretch wovens, which have easystretch, easy process, low shrinkage, friendly garment making, andexcellent recovery power and low growth.

SUMMARY OF THE INVENTION

One aspect includes methods for making composite yarns with two sets ofdifferent elastic core fibers, referred to as a double elastic compositeyarn. Also included are the double elastic composite yarns and thestretch fabrics and garments made from such yarns.

According to a first embodiment of the method, two sets of elasticfibers with different properties and a hard fiber are covered togetherto form a composite yarn, wherein the two sets of elastic fibers arestretched to different drafts of its original length during yarncovering process. The elastic fiber may be bare spandex yarn from 11 to560 dtex, and the hard fiber with a yarn count from 10 to 900 dtex. Onesuitable hard yarn is cotton. The elastic core fiber I and elastic corefiber II are independently selected from an elastomeric ornon-elastomeric fiber.

According to a second embodiment of the method, two sets of elasticfibers (elastic core fiber I and elastic core fiber II) with differentproperties and a hard fiber are covered together to form a compositeyarn, wherein the two sets of elastic fibers have different polymercompositions and with different stress-strain behaviors. The elasticfibers may be bare spandex yarn from 11 to 560 dtex, and the hard fiberwith a yarn count from 10 to 900 dtex. One suitable hard yarn is cotton.

According to a third embodiment of the method, two sets of differentelastic core fibers (elastic core fiber I and elastic core fiber II) anda hard fiber are covered together to form a composite yarn, wherein atleast one set of elastic core fibers is pre-covered elastic yarn.Another set of elastic core yarn may be bare spandex or pre-coveredelastic yarn. The bare spandex yarn denier is from 11 to 560 dtex, andthe hard fiber with a yarn count from 10 to 900 dtex. One suitable hardyarn is cotton.

According to a fourth embodiment of the method, two sets of differentelastic core fibers and a hard fiber are covered together to form acomposite yarn, wherein at least one elastic core fiber isno-elastomeric stretch fibers. Another set of elastic core yarn may bebare elastomeric, such as spandex. The bare spandex yarn denier is from11 to 560 dtex, and the hard fiber with a yarn count from 10 to 900dtex. One suitable hard yarn is cotton.

A fabric is made by using the double elastic yarn produced by one ofthese alternate methods. The double elastic yarn is used in at least onedirection of the fabric. Any forms of fabrics may be used, includingwovens, circular knits, warp knits and narrow fabrics. Furtherprocessing may include scouring, bleaching, dyeing, drying, sanforizing,singeing, de-sizing, mercerizing, and any combination of such steps. Thestretched fabric produced may be formed into a garment.

BRIEF DESCRIPTION OF THE FIGURES

The detailed description will refer to the following drawings, whereinlike numerals refer to like elements and wherein:

FIG. 1 is an illustrated of core spun yarn with two elastic cores FIG. 2is a schematic description of a core spinning apparatus with two draftdevices for two bare elastic fibers.

FIG. 3 is a schematic description of a core spinning apparatus with twodraft devices with weighted roll.

FIG. 4 is a schematic description of a core spinning apparatus with twodraft devices for one bare elastic fiber and one pre-covered elasticyarn.

DETAILED DESCRIPTION OF THE INVENTION

Elastomeric fibers are commonly used to provide stretch and elasticrecovery in woven fabrics and garments. “Elastomeric fibers” are eithera continuous filament (optionally a coalesced multifilament) or aplurality of filaments, free of diluents, which have a break elongationin excess of 100% independent of any crimp. An elastomeric fiber when(1) stretched to twice its length; (2) held for one minute; and (3)released, retracts to less than 1.5 times its original length within oneminute of being released. As used in the text of this specification,“elastomeric fibers” means at least one elastomeric fiber or filament.Such elastomeric fibers include but are not limited to rubber filament,biconstituent filament and elastoester, lastol, and spandex.

“Spandex” is a manufactured filament in which the filament-formingsubstance is a long chain synthetic polymer comprised of at least 85% byweight of segmented polyurethane.

“Elastoester” is a manufactured filament in which the fiber formingsubstance is a long chain synthetic polymer composed of at least 50% byweight of aliphatic polyether and at least 35% by weight of polyester.

“Biconstituent filament” a continuous filament or fiber including atleast two polymers adhered to each other along the length of thefilament, each polymer being in a different generic class, for example,an elastomeric polyetheramide core and a polyamide sheath with lobes orwings.

“Lastol” is a fiber of cross-linked synthetic polymer, with low butsignificant crystallinity, composed of at least 95 percent by weight ofethylene and at least one other olefin unit. This fiber is elastic andsubstantially heat resistant.

“Polyester bi-component filament” means a continuous filament comprisinga pair of polyesters intimately adhered to each other along the lengthof the fiber, so that the fiber cross section is for example aside-by-side, eccentric sheath-core or other suitable cross-section fromwhich useful crimp can be developed. The fabric made with this filament,such as Elasterell-p, PTT/PET bi-component fiber, has excellent recoverycharacteristics.

“No-elastomeric elastic fibers” means a stretch filament withoutcontaining elastomeric fiber. However, the recoverable stretch of suchyarn must be higher than 20% as tested by ASTM D6720 methods, such astextured PPT stretch filament, textured PET stretch filament,bi-component stretch filament fiber, or PBT stretch filament.

A “Pre-covered elastic yarn” is one surrounded by, twisted with, orintermingled with hard yarn before the core spun process. Thepre-covered elastic yarn that includes elastomeric fibers and hard yarnsis also termed a “pre-covered yarn” in the text of this specification.The hard-yarn covering serves to protect the elastomeric fibers fromabrasion during textile processes. Such abrasion can result in breaks inthe elastomeric fiber with consequential process interruptions andundesired fabric non-uniformities. Further, the covering helps tostabilize the elastomeric fiber elastic behavior, so that the elongationof pre-covered elastic yarn can be more uniformly controlled duringtextile processes than would be possible with bare elastomeric fibers.The pre-covered yarn also can increase the tensile modulus of the yarnand fabric, which is helpful to improve the fabric recovery power anddimensional stabilities.

The pre-covered yarns include: (a) single wrapping of the elastomerfibers with a hard yarn; (b) double wrapping of the elastomer fiberswith a hard yarn; (c) continuously covering (i.e., corespun orcore-spinning) an elastomer fiber with staple fibers, followed bytwisting during winding; (d) intermingling and entangling elastomer andhard yarns with an air jet; and (e) twisting an elastomer fibers andhard yarns together.

“Double elastic composite yarn” is a composite yarn comprising with twosets of elastic core fibers with single yarn, covered with hard staplefiber sheath. The term “double elastic yarn” is used interchangeablythroughout the specification.

The stretch fabric of the some embodiments includes double elastic corespun yarn in weft direction. In some embodiments, a fabric withunexpectedly high recovery properties was achieved, especially for highstretch fabrics. This was accomplished by the use of core spun yarncontaining with two different elastic fibers with different stretchproperties. Those of skill in the art will recognize that where weftstretch is desired, the fabric may include such core spun yarn withdouble elastic fibers in weft direction.

As demonstrated in FIG. 1, the double elastic yarn 8 according to thepresent invent will necessarily include two elastic filaments core:elastic core I (4, in FIG. 1) and elastic core II (6, in FIG. 1). Theelastic core filaments are surrounded, preferably along the entirety ofits length by a fibrous sheath 2 comprised of spun staple fibers.

One embodiment of a representative core spinning apparatus 40 is shownin FIG. 2. Two separated fiber draft devices 46 and 64 are installed onthe machine. During core spinning processing, elastic core filament I 48and elastic core filament II 60 are put on deliver roll 46 and 64separately and are combined with a hard yarn to form a composite corespun yarn. The core elastic filaments from tube 48 and tuber 60 areunwound in the direction of arrow 50 and 62 by the action ofpositively-driven feed rollers 46 and 64. The feed rollers 46 and 64serve as a cradle for the tube 48 and tube 60 and deliver the elasticfiber of yarn 52 and 66 at a pre-determined speed.

The hard fiber or yarn 44 is unwound from tube 54 to meet the elasticcore filament 52 and 66 at the set of front rollers 42. The combinedelastic core filaments 52, 66 and hard fiber 44 are core spun togetherat spinning device 56.

The elastic core filament I 52 and elastic core filament II 66 arestretched (drafted) before it enters the front rollers 42. The elasticfilaments are stretched through the speed difference between feedrollers 46 or 64 and front rollers 42. The delivery speed of the frontrollers 42 is greater than the speed of the feed rollers 46 and 64.Adjusting the speed of the feed rollers 46 and 64 gives the desireddraft or stretch ratio.

The stretch ratio is normally 1.01× times to 5.0× times (101× to 5.0×)compared to the un-stretched fiber. Too low a stretch ratio will resultin low quality yarns having grin-through and an un-centered elasticfilament. Too high a stretch ratio will result in breakage of theelastic filament and core void.

Another embodiment of a representative core spinning apparatus 40 isshown in FIG. 3. Elastic core I is bare elastic filaments 48, whileelastic core II 12 is pre-covered elastic yarn. The elastic core II fromtube 12 is unwound in the direction of arrow 62 by the action ofpositively-driven feed rollers 64. The weighted roll 66 serves tomaintain stable contact between the elastic core II and feed rollers 64in order to deliver the elastic core II of yarn 68 at a pre-determinedspeed. Other elements of FIG. 3 are as described for FIG. 2.

Another embodiment of a representative core spinning apparatus 40 isshown in FIG. 4. Elastic core I is bare elastic filaments 48, whileelastic core II 12 is pre-covered elastic yarn. The elastic core II fromtube 12 is taken off from end and then passes through tension controldevice and guide bar. The tension device serves to keep the yarn tensionstable at a pre-determined level. The stretch ratio for bare elasticfiber is normally 1.01× times to 5.0× times (1.01× to 5.0×) compared tothe un-stretched fiber. Other elements of FIG. 4 are as described forFIG. 2.

According to some embodiment of the method, two elastic fibers withdifferent properties and a hard fiber are covered together to form acomposite yarn, wherein the two elastic fibers are stretched todifferent drafts of its original length during yarn covering process.The draft of two elastic fibers can be selected between drafts 1.01×times to 5.0× times. For the two core elastic fibers with differentdeniers or different filament numbers, the stretch ratio of core elasticI and elastic core II could be different from each other, depending theelastic fiber performances and requirement of fabric quality. In manycases, one core is drafted more to provide high stretch performance,while another core is stretched less to provide the fabrics with lowshrinkage and high recovery power.

In conventional fabrics, if heat setting is not used to “set” thespandex, the fabric may have high shrinkage, excessive fabric weight,and excessive elongation, which may result in a negative experience forthe consumer. Excessive shrinkage during the fabric finish process mayresult in crease marks on the fabric surface during processing andhousehold washing. Creases that develop in this manner are frequentlyvery difficult to remove by ironing.

By using low draft in one of elastic core fiber, the high-temperatureheat setting step in the process can be avoided. This new process mayreduce heat damage to certain fibers (i.e. cotton) and thus may improvethe handle of the finished fabric. The fabrics of some embodiments maybe prepared in the absence of a heat setting step including where thefabrics will be prepared into garments. As a further benefit, heatsensitive hard yarns can be used in the new process to make shirting,elastic, fabrics, thus increasing the possibilities for different andimproved products. In addition, the shorter process has productivitybenefits to the fabric manufacturer.

It was unexpectedly found that the core spun yarn with two differentelastic core fibers has higher stretch and recovery power than the corespun yarn made from single core elastic filament with the same denier.For example, the core spun yarn with two core of 30d/3filament spandexplus 40D/4filament spandex, has more recovery power than a core spunmade from single core of 70D/5filament yarn under the same draft. So, wecan make the core spun yarn with higher stretch and higher recoverypower by using the same contents of the spandex.

Two elastic fibers with different properties could be used and arecovered together with hard fiber sheath to form a composite yarn,wherein the two elastic fibers could have different polymer compositionsand with different stress-strain behaviors. One example is to use twospandex fibers with different heatset efficiency together within onecore spun yarn, such as normal LYCRA® spandex fiber T162C and easy setLYCRA® fiber T562B. The fabric can be heatset at the temperature higherthan easy set LYCRA® fiber heatset temperature, but lower than normalLYCRA® fiber heatset temperature. So, the fabrics just get partialheatset which provide acceptable fabric shrinkage while good stretch andgrowth.

Another example is the core spun containing elastic core I with hightension modulus and elastic core II with low tension modulus. Elasticcore I provide the fabric with high recovery power and low fabricgrowth, while elastic core II with low modulus give the fabric with easystretch, lower shrinkage, resulting in the fabric with easy stretch,high holding force and high dimension stability. The elastic fibers withdifferent chemical composition also can be combined together with onecore spun yarn, such as polyolefin elastic fiber Lastol and spandex.Spandex fibers offer the high recovery power while Lastol fiberscontribute the good heat resistance and lower shrinkage performance.

The combination of elastic core I and elastic core II could be elasticbare fiber plus elastic bare fiber; or elastic bare fiber pluspre-covered elastic yarn, or pre-covered elastic yarn plus pre-coveredelastic yarn. The bare elastic fiber may be from about 11 dtex to about444 dtex (denier—about 10D to about 400D), including 11 dtex to about180 dtex (denier 10D to about 162D).

The pre-covered elastic yarn includes various types, such as singlewrapping of the elastomer fibers with a hard yarn; double wrapping ofthe elastomer fibers with a hard yarn; continuously covering (i.e.,core-spinning) an elastomer fiber with staple fibers, followed bytwisting during winding; intermingling and entangling elastomer and hardyarns with an air jet; and twisting an elastomer fibers and hard yarnstogether. The preferred pre-covered elastic yarn are spandex air jetcovered yarns with textured polyester and nylon filaments, such as 40Dor 70D spandex with 50D to 150D polyester air covered yarn. Thepre-covered elastic yarn is made in a separated machine before the corespun yarn process.

The pre-covered elastic yarn can be present in any desired amount, forexample from about 5 to about 35% weight percent based on total doubleelastic yarn weight. The linear density of the pre-covered yarn rangesfrom about 15 denier (16.5 dtex) to about 900 denier (990 dtex),including from about 30 denier to 300 denier (33 dtex to 330 dtex). Whenthe ratio of yarn denier between pre-covered yarn and total doubleelastic yarn is lower than 35%, the fabric has no substantial grinthrough. After the finishing process, two elastic core fibers, includingin pre-covered yarn, are invisible and untouchable.

The deniers of bare elastic fiber (prior to covering to form pre-coveredyarn) may be from about 11 dtex to about 444 dtex (denier—about 10D toabout 400D), including 11 dtex to about 180 dtex (denier 10D to about162D). During the pre-covering process, the elastic fiber is draftedbetween 1.1× to 6× its original length. In pre-covering, the elasticfiber is pre-covered with one or more hard yarns, with hard yarn denierfrom 10 to 600 deniers.

Another combination of elastic core fiber I and elastic core fiber IIcould be one set of elastic bare fiber plus another set ofno-elastomeric elastic fibers. The no-elastomeric elastic fibers can betextured PET stretch filament, textured PPT stretch filament,bi-component fiber, or PBT stretch fiber. It was surprise to find thatwhen the no-elastomeric elastic fiber with recoverable stretch higherthan 20% were used as one of the elastic core fibers, the performance ofthe core spun yarn and the fabric change dramatically. The fabrics havehigh stretch and high recovery power. The linear density of theno-elastomeric elastic fibers can range from about 15 denier (16.5 dtex)to about 450 denier (495 dtex), including from about 30 denier to 150denier (33 dtex to 165 dtex). When the denier is too high, the fabriccould have substantial grin through.

The elastomer fiber content with double elastic core spun yarns arebetween about 0.1% to about 20%, including from about 0.5% to about 15%,and about 5% to about 10% based on the weight of the yarn. Elastomericfiber content within the fabric may be from about 0.01% to about 10% byweight based on the total fabric weight, including from about 0.5% toabout 5%.

The staple sheath fibers in double elastic yarn can be nature fibers,such as, cotton, wool or linen. They also can be the staple man made orsynthetic fibers of mono component polyethylene terephthalate) andpoly(trimthylene terephthalate) fiber, polycaprolactam fiber,poly(hexamethylene adipamide) fibers acrylic fibers, modacrylic, acetatefibers, Rayon fibers, Nylon and combinations thereof.

Such double elastic yarns can be used for making a stretch fabric wherevarious weave patterns can be applied, including plain, poplin, twill,oxford, dobby, sateen, satin and combinations thereof. The fabrics ofsome embodiments may have an elongation from about 10% to about 45% inthe warp or/and weft direction. The fabrics may have shrinkage of about15% or less after washing. The stretch woven fabric may have anexcellent cotton hand feel. Garments may be prepared from the fabricsdescribed herein.

The warp yarn can be the same as, or different from, the weft yarns. Thefabric can be weft-stretch only, or it can be bi-stretch, in whichuseful stretch and recovery properties are exhibited in both the warpand weft directions.

Air jet loom, rapier loom, projectile loom, water jet loom and shuttleloom can be used. Dyeing and finishing process are important inproducing a satisfactory fabric. The fabric can be finished incontinuous range processes and the piece dye jet processes. Conventionalequipment found in a continuous finishing plant and piece dye factoriesare usually adequate for processing. The normal finishing processsequences include preparation, dyeing and finishing. In preparation anddyeing process, including in singing, desizing, scouring, bleaching,mercerizing and dyeing, normal processing methods for elastic wovens areusually satisfactory.

Analytical Methods: Yarn Recoverable Stretch

The recoverable Stretch of elastic fibers used in the Examples wasmeasured as follows. Each yarn sample was formed into a skein of5000+/−5 total denier (5550 dtex) with a skein reel at a tension ofabout 0.1 gpd (0.09 dN/tex). The skein was conditioned at 70° F. (+/−2°F.) (21°+/−1° C.) and 65% (+/−2%) relative humidity for a minimum of 16hours. The skein was hung substantially vertically from a stand, a 6mg/den (5.4 mg/dtex) weight (e.g. 30 grams for a 5550 dtex skein) washung on the bottom of the skein, the weighted skein was allowed to cometo an equilibrium length, and the length of the skein was measured towithin 1 mm and recorded as “C_(b)”. The 5.4 mg/dtex weight was left onthe skein for the duration of the test. Next, a 1030 gram weight (206mg/d; 185.4 mg/dtex) was hung from the bottom of the skein, and thelength of the skein was measured to within 1 mm and recorded as “L_(b)”.

The 1030 g weight was removed, and the skein was then immersed intoboiling water for 10 minutes at 100° C. degree water, after which theskein were removed from the water and conditioned as above for 16 hours.This step is designed to simulate commercial fabric relaxation process,which is one way to develop the fabric stretch. The length of the skeinwas measured as above, and its length was recorded as “C_(a)”. The1030-gram weight was again hung from the skein, and the skein length wasmeasured as above and recorded as “L_(a)”. The after relaxation Yarnrecoverable stretch (percent), “CC_(a)”, was calculated according to theformula CC_(a)=100×(L_(a)−C_(a))/L_(a). Yarn shrinkage was calculatedaccording to formula Cs (%)=100×(L_(b)−L_(a))/L_(b)

Woven Fabric Elongation (Stretch)

Fabrics are evaluated for % elongation under a specified load (i.e.,force) in the fabric stretch direction(s), which is the direction of thecomposite yarns (i.e., weft, warp, or weft and warp). Three samples ofdimensions 60 cm×6.5 cm were cut from the fabric. The long dimension (60cm) corresponds to the stretch direction. The samples are partiallyunraveled to reduce the sample widths to 5.0 cm. The samples are thenconditioned for at least 16 hours at 20° C.+/−2° C. and 65% relativelyhumidity, +/−2%.

A first benchmark was made across the width of each sample, at 6.5 cmfrom a sample end. A second benchmark was made across the sample widthat 50.0 cm from the first benchmark. The excess fabric from the secondbenchmark to the other end of the sample was used to form and stitch aloop into which a metal pin could be inserted. A notch was then cut intothe loop so that weights could be attached to the metal pin.

The sample non-loop end was clamped and the fabric sample was hungvertically. A 17.8 Newton (N) weight (4 LB) is attached to the metal pinthrough the hanging fabric loop, so that the fabric sample is stretchedby the weight. The sample was “exercised” by allowing it to be stretchedby the weight for three seconds, and then manually relieving the forceby lifting the weight. This cycle was carried out three times. Theweight was allowed then to hang freely, thus stretching the fabricsample. The distance in millimeters between the two benchmarks wasmeasured while the fabric was under load, and this distance isdesignated ML. The original distance between benchmarks (i.e.,unstretched distance) was designated GL. The % fabric elongation foreach individual sample as calculated as follows:

% Elongation (E %)=((ML−GL)/GL)×100

The three elongation results were averaged for the final result.

Woven Fabric Growth (Unrecovered Stretch)

After stretching, a fabric with no growth would recover exactly to itsoriginal length before stretching. Typically, however, stretch fabricswill not fully recover and will be slightly longer after extendedstretching. This slight increase in length is termed “growth.”

The above fabric elongation test must be completed before the growthtest. Only the stretch direction of the fabric was tested. For two-waystretch fabric both directions were tested. Three samples, each 55.0cm×6.0 cm, were cut from the fabric. These were different samples fromthose used in the elongation test. The 55.0 cm direction shouldcorrespond to the stretch direction. The samples were partiallyunraveled to reduce the sample widths to 5.0 cm. The samples wereconditioned at temperature and humidity as in the above elongation test.Two benchmarks exactly 50 cm apart were drawn across the width of thesamples.

The known elongation % (E %) from the elongation test was used tocalculate a length of the samples at 80% of this known elongation. Thiswas calculated as

E (length) at 80%=(E %/100)×0.80×L,

where L was the original length between the benchmarks (i.e., 50.0 cm).Both ends of a sample were clamped and the sample was stretched untilthe length between benchmarks equaled L+E (length) as calculated above.This stretch was maintained for 30 minutes, after which time thestretching force was released and the sample was allowed to hang freelyand relax. After 60 minutes the % growth was measured as

% Growth=(L2×100)/L,

where L2 was the increase in length between the sample benchmarks afterrelaxation and L was the original length between benchmarks. This %growth was measured for each sample and the results averaged todetermine the growth number.

Woven Fabric Shrinkage

Fabric shrinkage was measured after laundering. The fabric was firstconditioned at temperature and humidity as in the elongation and growthtests. Two samples (60 cm×60 cm) were then cut from the fabric. Thesamples were taken at least 15 cm away from the selvage. A box of foursides of 40 cm×40 cm was marked on the fabric samples.

The samples were laundered in a washing machine with the samples and aloading fabric. The total washing machine load was 2 kg of air-driedmaterial, and not more than half the wash consisted of test samples. Thelaundry was gently washed at a water temperature of 40° C. and spun. Adetergent amount of 1 g/l to 3 g/l was used, depending on waterhardness. The samples were laid on a flat surface until dry, and thenthey were conditioned for 16 hours at 20° C.+/−2° C. and 65% relativehumidity+/−2% rh.

Fabric sample shrinkage was then measured in the warp and weftdirections by measuring the distances between markings. The shrinkageafter laundering, C %, was calculated as

C %=((L1−L2)/L1)×100,

where L1 was the original distance between markings (40 cm) and L2 isthe distance after drying. The results are averaged for the samples andreported for both weft and warp directions. Negative shrinkage numbersreflect expansion, which was possible in some cases because of the hardyarn behavior.

Fabric Weight

Woven Fabric samples were die-punched with a 10 cm diameter die. Eachcut-out woven fabric sample was weighed in grams. The “fabric weight”was then calculated as grams/square meters.

EXAMPLES

The following examples demonstrate the present invention and itscapability for use in manufacturing a variety of fabrics. The inventionis capable of other and different embodiments, and its several detailsare capable of modifications in various apparent respects, withoutdeparting from the scope and spirit of the present invention.Accordingly, the examples are to be regarded as illustrative in natureand not as restrictive.

For each of the following denim fabric examples, 100% cotton open endspun yarn or ring spun was used as warp yarn. For denim fabrics, theyincluded two count yarns: 7.0 Ne OE yarn and 8.5 Ne OE yarn withirregular arrangement pattern. The yarns were indigo dyed in rope formbefore beaming. Then, they were sized and made the weaving beam. Forbottom weight fabrics, the warp yarn are 20Ne 100% cotton ring spunyarn. They were sized and made the weaving beam.

Table 1 lists four examples of core spun yarn with traditional oneelastic core filament and innovative yarn containing two sets of elasticcores.

Several core spun yarns with double elastic core fibers were used asweft yarn. Various elastic core fibers, including bare spandex,pre-covered polyester/LYCRA® spandex fiber or pre-covered nylon/spandexyarn were used as in the core. Table 2 lists the materials and processways that were used to make the core spun yarn for each example. Table 3shows the detail fabric structure and performance summary for eachfabric. Lycra® spandex are available from Invista, s. á. r. L., Wichita,Kans. For example, in the column headed spandex 40D means 40 denier;3.5× means the draft of the Lycra® imposed by the core spinning machine(machine draft). In the column headed ‘Rigid sheath Yarn’, 20's is thelinear density of the spun yarn as measured by the English Cotton CountSystem. The rest of the items in Table 1 and table 2 are clearlylabeled.

Stretch woven fabrics were subsequently made, using the core spun yarnof each example in Table 2. Table 3 summarizes the yarns used in thefabrics, the weave pattern, and the quality characteristics of thefabrics. Some additional comments for each of the examples are givenbelow. Unless otherwise noted, the fabrics were woven on a Donierair-jet or rapier loom. Loom speed was 500 picks/minute. The widths ofthe fabric were about 76 and about 72 inches in the loom and greigestate respectively. The loom has double weaving beam capacity.

Each greige fabric in the examples was finished by a jiggle dye machine.Each woven fabric was pre-scoured with 3.0 weight % Lubit®64 (SybronInc.) at 49° C. for 10 minutes. Afterwards it was de-sized with 6.0weight % Synthazyme® (Dooley Chemicals. LLC Inc.) and 2.0 weight %Merpol® LFH (E. I. DuPont Co.) for 30 minutes at 71° C. and then scouredwith 3.0 weight % Lubit® 64, 0.5 weight % Merpol® LFH and 0.5 weight %trisodium phosphate at 82° C. for 30 minutes. Fabric finishing wasfollowed by dry in a tente frame at 160° C. for 1 minute.

TABLE 1 Examples of yarns with double elastic core fibers ElasticElastic Elastic Elastic Elastic Elastic Yarn Core Rigid Core I Core ICore I Core II Core II Core II Twist level, Cotton spun yarn Core sheathfiber fiber fiber fiber fiber fiber twisters Roving recoverable spunyarn Example yarn types deniers draft types denier draft per inch draftStretch, % Shrinkage, % Yarn A 16′ T162B 44/3f 3.5X No No No 18 22X17.71 2.1 cotton LYCRA ® dtex fiber (40D) Yarn B 16′ T162B 22/2f 3.5XT162B 22/2f 3.5X 18 22X 20.63 2.4 cotton LYCRA ® dtex LYCRA ® dtex fiber(20D) fiber (20D) Yarn C 16′ T162B 77/5f 3.8X No No No 18 22X 38.71 2.28cotton LYCRA ® dtex fiber (70D) Yarn D 16′ T162B 44/3 3.8X T162B 33/3f3.8X 18 22X 40.88 2.33 cotton LYCRA ® dtex LYCRA ® dtex fiber (40D)fiber (30D)

TABLE 2 Weft yarn description Elastic Elastic Elastic Elastic ElasticYarn Core Rigid Core I Core I Core I Core II fiber Twist level, Cottonspun yarn Core sheath fiber fiber fiber fiber draft in twisters Rovingrecoverable spun yarn Example yarn types deniers draft types Core II perinch draft Stretch Shrinkage 1 20′ T162B 44 dtex 3.5X No No 18 22 17.241.79 cotton LYCRA ® (40D) fiber 2 20′ T162B 44 dtex 3.5X 40D T162B 1.8X18 22 47.22 1.25 cotton LYCRA ® (40D) LYCRA ® fiber fiber 3 20′ T162B 44dtex 3.5X 40D T562B 3.5X 18 22 62.24 1.68 cotton LYCRA ® (40D) Easy Setfiber LYCRA ® fiber 4 16′ T162B 44 dtex 3.5X 40D 3.6X 18 22 36.6 1.2cotton LYCRA ® (40D) polyolefin fiber elastic fiber 5 20′ T162B 44 dtex1.8X Pre-covered 3.2X 18 22 44.2 2.07 cotton LYCRA ® (40D) 40D T162Cfiber LYCRA ® fiber with 40D/34F Nylon 6 20′ T162B 44 dtex 3.5XPre-covered 3.2X 18 22 58.04 2.01 cotton LYCRA ® (40D) 40D T162C fiberLYCRA ® fiber with 40D/34F Nylon 7 16′ T162B 44 dtex 3.5X Pre-covered1.8X 16 16 36.29 2.63 cotton LYCRA ® (40D) 40D T162C fiber LYCRA ® fiberwith 50D/24F polyester 8 16′ T162B 44 dtex 3.5X Pre-covered 2.6X 16 1649.3 2.5 cotton LYCRA ® (40D) 40D T162C fiber LYCRA ® fiber with 50D/24Fpolyester 9 16′ T162B 44 dtex 3.5X PBT Stretch 1.15X  16 16 24.6 2.7cotton LYCRA ® (40D) polyester fiber

TABLE 3 Fabric Example List Base Fabric on loom Width Finished FabricFabric Fabric Fabric Warp weaving (warp EPI × on fabric width, weightStretch, Growth, Shrinkage, % Example Weft yarn yarn pattern weft PPI)loom inch OZ/Y{circumflex over ( )}2 % % (warp × weft) 1 20s cotton +3.5X 20s 3/1 RHT 96 × 56 76 50.5 8.95 37.6 8.7 −0.91 × −0.91 LYCRA ®fiber cotton 2 20s cotton + 3.5X 20s 3/1 RHT 96 × 56 76 50.5 8.88 35.46.4 −1.57 × −0.13 LYCRA ® fiber + cotton 1.8X LYCRA ® fiber 3 20scotton + 3.5X 20s 3/1 RHT 96 × 56 76 50.2 9.19 38.4 7.9 −1.31 × −0.65LYCRA ® fiber + cotton 3.5X LYCRA ® fiber 4 16s cotton + 3.5X 7.0′ OE +3/1 RHT 64 × 54 72 55.5 11.39 47.8 6.5 −2.21 × −0.91 LYCRA ® fiber +8.4′ OE 40D polyolefin cotton elastic fiber indigo 5 16s cotton + 1.8X20s 3/1 RHT 96 × 56 76 50.5 8.79 35.9 5.3 −1.31 × −0.65 LYCRA ® fiber +cotton 3.2X pre-covered 40D LYCRA ® fiber 6 16s cotton + 3.5X 20s 3/1RHT 96 × 56 76 50.5 8.96 37.8 5.9     0 × −1.96 LYCRA ® fiber + cotton3.2X pre-covered 40D LYCRA ® fiber 7 16s cotton + 3.5X 7.0′ OE + 3/1 RHT64 × 54 72 56 12.80 35.3 3.5 −1.31 × −0.65 LYCRA ® fiber + 8.4′ OE 1.8Xpre-covered cotton 40D LYCRA ® indigo fiber 8 16s cotton + 3.5X 7.0′OE + 3/1 RHT 64 × 54 72 54.7 13.27 40.4 3.9 −1.31 × −0.65 LYCRA ®fiber + 8.4′ OE 2.6X pre-covered cotton 40D LYCRA ® indigo fiber 9 16scotton + 3.5X 7.0′ OE + 3/1 RHT 64 × 54 72 55.2 10.79 40.7 6 −2.10 ×−0.85 LYCRA ® fiber + 8.4′ OE 1.15X PBT fiber cotton indigo

Example Yarn A Typical Core Spun Yarn with One Elastic Core Fiber

This is not an innovative yarn. This core spun yarn is 16Ne with one 40dLYCRA® spandex fiber covered by cotton sheath. The draft of the LYCRA®fiber is 3.5× during covering process. The cotton twist level TM is 18twisters per inch. This yarn has 17.71% recoverable stretch after boiloff.

Example Yarn B Core Spun Yarn with Two Core Elastic Fibers

The core spun yarn is 16Ne with two sets of LYCRA® spandex fiber coveredby cotton sheath. Elastic core I fiber is 20D T162B and Elastic core IIfiber is 20D T162B as well. The total denier of the elastic finer is 40denier. The draft of the LYCRA® fiber is 3.5× during covering process.The cotton twist level TM is 18 twisters per inch. Therefore, this corespun yarn has the same structure with Example Yarn A, including in yarncount, LYCRA® fiber denier and yarn twist level, except with 2 sets ofcore elastic filaments instead of one end of core spun yarn. Therecoverable stretch of this yarn is 20.63%, which has 2.92 unit percenthigher than yarn in sample A. That means the yarn with two sets offilaments core has high recoverable stretch than the yarn with one setof filament core under the same content of spandex. In this way, theinnovative yarn can provide high stretch and high recovery power for thefabrics by using the same amount of elastic fibers.

Example Yarn C Typical Core Spun Yarn with One Elastic Core Fiber

This is not an innovative yarn. The core spun yarn is 16Ne with one 70dLYCRA® spandex fiber covered by cotton sheath. The draft of the LYCRA®fiber is 3.8× during covering process. The cotton twist level TM is 18twisters per inch. This yarn has 38.71% recoverable stretch after boiloff and the yarn have 2.28 shrinkage.

Example Yarn D Core Spun Yarn with Two Core Elastic Fibers

The core spun yarn is 16Ne with two sets of LYCRA® spandex fiberscovered by cotton sheath. The elastic core I fiber is 30D T162B andelastic core II fiber is 40D T162B. The total denier of the elasticfiner is 70 denier. The draft of both LYCRA® fiber is 3.8× duringcovering process. The cotton twist level TM is 18 twisters per inch.Therefore, this core spun yarn has the same structure with Example YarnC, except with 2 sets of core elastic filaments instead of one set ofcore spun yarn. The recoverable stretch of this yarn is 40.88%, whichhas 2.17 unit percent higher than yarn sample C. That shows that theyarn with two sets of filaments core has high recoverable stretch thanthe yarn with one set of filament core under the same content ofspandex. In this way, the innovative yarn can provide high stretch andhigh recovery power for the fabrics by using the same amount of elasticfibers.

Example 1 Typical Stretch Woven Bottom Weight Fabric

This is a comparison example, not according to the invention. The warpyarn was 40/2 Ne count of ring spun yarn. The weft yarn was 20 Ne cottonwith 40D Lycra® core spun yarn. Lycra® draft is 3.5×. This weft yarn wasa typical stretch yarn used in typical stretch woven khakis fabrics.Loom speed was 500 picks per minute at a pick level 56 Picks per inch.Table 3 summarizes the test results. The test results show that afterfinishing, this fabric had weight (8.95 g/m²), stretch (37.6%), width(50.5 inch), weft wash shrinkage (0.91%) and fabric growth (8.7%). Thedata indicate that this combination of stretch yarns and fabricconstruction caused high fabric growth.

Example 2 Stretch Fabric with Double Elastic Fibers

This sample had the same fabric structure as in example 1. The onlydifference was the use of 20s weft yarn containing double core elasticfibers: 40D LYCRA® fiber with 3.5× draft and 40d LYCRA® fiber with 1.8×draft. The warp yarn was 40/2 Ne ring spun cotton. The loom speed was500 picks/minute at 56 picks per inch. Table 3 summarizes the testresults. It is clearly shows that this sample has similar stretch butlower fabric growth level (6.4%). Therefore, by using two differentdrafts of elastic core fibers within the same yarn, the covered yarn andthe fabric can achieve different characters. For example, the high draftin elastic core I fiber give the fabric with high stretch, while thelower draft in elastic core II fibers give the fabric with low growth,high recover but not increase the fabric shrinkage. In this way, thefabrics with high stretch, high recovery and low shrinkage can beproduced.

Example 3 Stretch Fabric Containing Double Elastic Fibers

This sample had the same fabric structure as in example 1. The onlydifference was the use of core spun yarns in weft: 40D T162B LYCRA®fiber with 3.5× draft and 40d Easyset LYCRA® fiber with 3.5× draft. Thewarp yarn was 20 Ne 100% cotton ring spun yarn. 3/1 twill weavingpattern was applied. The finished fabric had weight (9.19 g/m²), 38.4.0%stretch and 7.9% growth in the weft direction. It is clear shows,Easyset LYCRA® fiber in elastic core II maintain the fabrics stretchlevel while reducing the fabric growth from 8.7% in example 1 to 7.9%.

Easyset LYCRA® fiber can be heatset at about 170° C. degree, which isabout 20° C. lower than the heatset temperature of T162B LYCRA® fiber.Therefore, when the fabrics are heatset in a temperature between 170° C.and 190° C., the fabric got partially heatset. Only Easyset LYCRA® fiberis set and T162B is not set. In this way, the fabric keeps betterstretch and recovery while the shrinkage keep under certain level.

Example 4 Stretch Fabric with Spandex and Elastic Polyolefin Fiber

The warp yarn was 7.0 Ne count and 8.4 Ne count mixed open end yarn. Thewarp yarn was indigo dyed before beaming. The weft yarn is 16Ne corespun yarn with 40D T162B Lycra® spandex and 40D elastic polyolefinfiber. The Lycra® fiber and elastic polyester fiber were drafted 3.5×during covering process. Table 3 lists the fabric properties. The fabricmade from such yarns exhibited good cotton hand, good stretch (47.8%)and good recovery (6.5% growth). All test results indicate that thecombination of spandex and elastic polyolefin filaments can produce goodfabric stretch and growth. Fabric has no grin through. Elastic filamentscan't be seen from both fabric surface and fabric back.

As compared with spandex, elastic polyolefin fiber or Lastol fiber haslower recovery power, but better heat resistance, better chemicalresistance, low fabric shrinkage and good cotton hand touch feeling. Thefabrics contained with both spandex and elastic polyolefin can providegood stretch and good recovery with better heat resistance, lowershrinkage and better chemical resistance, such as chlorine resistance inswimming pool and denim bleaching processes.

Example 5 Stretch Fabric Containing Spandex and Pre-Covered Elastic Yarn

This sample had the same fabric structure as example 1. The differencewas the core spun yarn in weft direction, which containing one bare 40DLYCRA® fiber and one pre-covered elastic yarn (40D/34f Nylon/40D Lycra®air covered yarn) in the core of the yarn. The draft of bare 40D LYCRA®fiber is 1.8× and the draft of LYCRA® fiber in pre-covered elastic yarnis 3.2×. This fabric used the same warp and structure as Example 1.Also, the weaving and finishing process were the same as Example 1.Table 3 summarizes the test results. We can see that this sample hadgood stretch (35.9%), good weft direction wash shrinkage (0.65%) andgood fabric growth (5.3%). The fabric appearance and handle wasexcellent. After adding pre-covered elastic yarn (40D/34f Nylon/40DLycra® fiber AJY yarn), the fabric growth remarkably reduced.

Example 6 Stretch Fabric Containing Spandex and Pre-Covered Elastic Yarn

This sample had the same fabric structure as in example 5. The onlydifference was the draft of 40D bare LYCRA® fiber during coveringprocess. The bare LYCRA® fiber draft is 3.5× while it was 1.8× inExample 5. The fabric weight was 8.96 OZ/yd², and the weft elongationwas 37.8%. The Fabric had very low growth (5.9%) in weft. This samplefurther confirms that adding additional elastic composite yarn canproduce high performance stretch fabrics with low growth. Double elasticyarn makes the fabric growth to 5.9% from 8.7% in Example 1. As comparedwith Example 5, the draft increase also results in higher weight andstretch.

Example 7 Stretch Denim Containing Spandex and Pre-Covered Elastic Yarn

This example had the same warp yarn and same fabric structure as Example4. The warp yarn was 7.0 Ne count and 8.4 Ne count mixed open end yarn.The warp yarn was indigo dyed before beaming. The weft yarn is 16Ne corespun yarn with 40D Lycra® spandex and 50D/24f polyester 40D LYCRA® fiberair jet covered yarn. Lycra® draft is 3.5× and 1.8× in bare andcomposite core. This sample is an innovation fabric. Loom speed was 500picks per minute at a pick level 44 Picks per inch. Table 3 summarizesthe test results. The test results show that after washing, this fabrichad weight (12.80 OZ/Y²), 35.3% weft stretch and 3.5% growth in weft.

Example 8 Stretch Denim Containing Spandex and Pre-Covered Elastic Yarn

This example had the same warp yarn and same fabric structure as Example7, except the LYCRA® fiber draft in pre-covered elastic yarn (2.6× draftin Example 8 vs. 1.8× draft in example 7)). Table 3 summarizes the testresults. It is clear that this sample had good stretch (weft 40.4%) ascompared with sample 7.

Example 9 Stretch Fabric with Spandex and PBT Stretch Fiber

This example had the same warp yarn and same fabric structure as Example7 and 8, except using 50D/26f PBT stretch fiber as elastic core IIfiber. This bare 50D/26f PBT fiber have 40.23% recoverable stretch and3.44% shrinkage tested with ASTM D6720 Method. The elastic core I Lycra®fiber was drafted 3.5× during covering process. Table 3 lists the fabricproperties. The fabric made from such yarns exhibited good cotton hand,good stretch (40.7%) and good recovery (6.0% growth). All test resultsindicate that the combination of spandex and no-elastomeric stretchfilaments can produce good fabric stretch and growth. Fabric has no grinthrough; elastic filaments can't be seen from both fabric surface andfabric back.

What is claimed is:
 1. An article comprising a core spun yarncomprising: a) a sheath of hard fibers; b) one set of elastic fiber(elastic core fiber I); and c) a second set of elastic fiber (elasticcore fiber II); wherein the elastic core fiber I and the elastic corefiber II have different elastic properties.
 2. The article of claim 1,wherein the elastic core fiber I and elastic core fiber II havedifferent deniers or different filaments.
 3. The article of claim 1,wherein the elastic core fiber I and elastic core fiber II havedifferent drafts.
 4. The article of claim 1, wherein the elastic corefiber I and elastic core fiber II have different polymer compositions.5. The article of claim 1, wherein at least one elastic core fibercomprises elastomeric fiber having denier of about 10 denier to about450 denier.
 6. The article of claim 5, wherein at least one elastic corefiber comprises spandex fiber.
 7. The article of claim 1, wherein atleast one elastic core fiber comprises elastic polyolefin fiber havingdenier of about 10 denier to about 450 denier.
 8. The article of claim7, wherein the elastic polyolefin fiber is lastol fiber.
 9. The articleof claim 1, wherein at least one set of elastic core yarns arepre-covered elastic yarn having denier of about 15 denier to about 300denier.
 10. The article of claim 9, wherein the pre-covered elasticyarns include a covering selected from the group of air covered yarn,single wrapped yarn, double wrapped yarn, and combinations thereof. 11.The article of claim 9, wherein the pre-covered elastic yarn is apolyester and spandex air covered yarn.
 12. The article of claim 1,wherein at least one elastic core fiber includes a non-elastomericelastic fiber having a denier of about 15 to about 450 denier.
 13. Thearticle of claim 12, wherein the non-elastomeric elastic yarn isselected from the group of filaments with yarn recoverable stretchhigher than 20% tested with ASTM D6720-07 method
 14. The article ofclaim 13 wherein said non-elastomeric elastic yarn comprises at leastone fiber selected from the group consisting of polyester, nylon, PTTfiber, PBT fiber, bi-component fiber, and combinations thereof.
 15. Thearticle of claim 1, wherein the sheath of hard fibers is selected fromthe group consisting of wool, linen, silk, polyester, nylon, olefin,cotton, and combinations thereof.
 16. An article comprising a wovenfabric having warp yarns and weft yarns, wherein at least one of thewarp yarns and weft yarns includes a core spun yarn comprising: a) asheath of hard fibers; b) one set of elastic fiber (elastic core fiberI); and c) a second set of elastic fiber (elastic core fiber II);wherein the elastic core fiber I and the elastic core fiber II havedifferent elastic properties.
 17. The article of claim 16, wherein thefabric has stretch in the weft direction between about 10 and about 45%.18. The article of claim 16, wherein said fabric comprises a garment.19. A method of making an article comprising a woven fabric having warpyarns and weft yarns. Either warp yarn or weft yarn or both warp andweft yarns have core spun yarn, wherein, the core spun yarn comprising:a) a sheath of hard fibers; b) one set of elastic fiber (elastic corefiber I); and c) a second set of elastic fiber (elastic core fiber II);wherein the elastic core fiber I and the elastic core fiber II havedifferent elastic properties.
 20. A stretch fabric comprising a corespun yarn comprising: a) a sheath of hard fibers; b) one set of elasticfiber (elastic core fiber I); and c) a second set of elastic fiber(elastic core fiber II); wherein the elastic core fiber I and theelastic core fiber II have different elastic properties.
 21. The articleof claim 20, wherein the fabric is woven, or warp knit, or circular knitfabric.